1. Field of the Invention
The present invention generally relates to an integrated cable modem that is configured on a common integrated circuit (IC) substrate, such as a silicon substrate.
2. Background Art
Television signals are transmitted at radio frequencies (RF) using terrestrial, cable, or satellite transmission schemes. Terrestrial and cable TV signals are typically transmitted at frequencies of approximately 57 to 860 MHz, with 6 MHz channel spacings in the United States and 8 MHz channel spacing in Europe. Satellite TV signals are typically transmitted at frequencies of approximately 980 to 2180 MHz.
Regardless of the transmission scheme, a tuner is utilized to select and down-convert a desired channel from the TV signal to an intermediate frequency (IF) signal or a baseband signal, which is suitable for processing and display on a TV or computer screen. The tuner should provide sufficient image rejection and channel selection during down-conversion as is necessary for the specific application. Historically, the National Television Standards Committee (NTSC) sets standards for television signal transmission, reception, and display. To process a NTSC signal, it is preferable that the tuner have a high-level of image rejection. However, more or less image rejection can be required for non-NTSC signals depending on the specific application and the corresponding display requirements. The output of the tuner can be coupled to a cable modem or to an integrated set-top box.
Furthermore, in a cable modem, the upstream path typically includes a power amplifier to amplify the upstream signal from the user for transmission over the cable.
In conventional systems, both the tuner IC and the power amplifier IC are typically implemented on separate substrates from the cable modem IC, where the cable modem IC typically includes the digital portions of the cable modem. Therefore, a cable modem assembly typically includes at least 3 substrates, namely, the tuner IC, the power amplifier IC, and the cable modem IC.
What is needed is a single chip configuration for the cable modem or a set-top box so that the tuner and the upstream power amplifier are integrated with the cable modem or the set-top box.